Method for switching control for an electric vehicle

Abstract

Method (400, 500) for shift control of an electric vehicle (100), comprising: detecting (404, 504) a shift operation for a multi-gear transmission (112) with at least one actuated clutch (114, 118) for selectively effecting a gear ratio change, wherein the multi-gear transmission (112) is designed to receive a first motor torque from a first electric motor (104) and to deliver a first axle torque to a first axle (106); actuating (508) the at least one actuated clutch (114, 118) to effect the change in the gear ratio, thereby generating a first axle torque oscillation in the first axle (106);Modulating (408) a second electric motor (108) to generate a second axis torque oscillation in a second axis (110) sufficient to counteract the first axis torque oscillation in the first axis (106) to reduce vehicle acceleration oscillation of the electric vehicle (100); Determining (406, 506) a percentage travel of an accelerator pedal (124) when the shift operation is detected; Retrieving (506) a second electric motor calibration correlated with the determined percentage travel of the accelerator pedal (124); and Applying (510) the second electric motor calibration when modulating the second electric motor (108) to generate the second axis torque oscillation in the second axis (110).

Description

Technical area The present disclosure relates to a method for shift control for multi-gear electric vehicles, in particular to a method for controlling upshifting during start-up for electric vehicles with a front electric motor driving a front axle and a rear electric motor driving a rear axle. introduction The trend in the automotive industry is moving towards the production and sale of electric vehicles. Electric vehicles are popular with car buyers because they produce no greenhouse gases and no harmful particulate emissions from their exhaust. Compared to conventional vehicles with combustion engines, electric vehicles are inherently fuel-efficient, even when powered by electricity from non-renewable sources such as fossil fuels. To further increase the fuel efficiency and performance of electric vehicles, the electric motors are equipped with multi-stage transmissions. This multi-stage transmission can be a two-speed gearbox with a simple planetary gear set and clutches configured to selectively deliver a first and second gear ratio to a drive axle. With the increasing popularity of electric vehicles, the demand for greater safety and performance is also rising. Electric vehicles are equipped with multiple motors that enable all-wheel drive (AWD) or four-wheel drive (4WD) to enhance safety in adverse weather conditions and improve off-road performance. In wet or icy road conditions, AWD / 4WD drive systems can selectively distribute torque to the axles with traction wheels to increase safety. In one example of such an AWD / 4WD system for an electric vehicle, a first electric motor is used to drive the front axle and a second electric motor is used to drive the rear axle. In the example AWD / 4WD electric vehicle, either the first or second electric motor can be the dedicated drive motor, also known as the main motor, for propelling the vehicle, while the other electric motor can be an auxiliary drive motor. Both the main and auxiliary motors engage when torque is required for both the front and rear axles. A multi-gear transmission can be coupled to the main motor to provide additional gear ratios and increase the drive power and lifespan of the electric motor. In electric vehicles with a multi-speed transmission where gear changes occur via a clutch shift—that is, when a first clutch disengages the first gear and a second clutch engages the second gear to effect a gear change—it is not uncommon for the vehicle to experience a oscillation in acceleration during the clutch shift. This oscillation is perceived by the vehicle occupants as a shaking and / or vibration, which is considered a sign of poor transmission performance. This brief oscillation in acceleration is more noticeable during upshifts when the transmission is engaged. DE 10 2007 023 164 A1 describes a method for operating a hybrid drive of a vehicle, in particular a motor vehicle, with at least one internal combustion engine and at least one first electric machine as drive machines of a first drive train of the vehicle and an associated first transmission, wherein the total torque of the drive machines is adjusted when the transmission is shifted in order to reduce the load on the transmission and / or to change speeds according to the new gear ratio and / or the torque gradient of the drive machines during a transition between traction and deceleration is limited to a predefinable maximum torque gradient of the resulting total torque of the drive machines of the first drive train.It is intended that the additional electrical energy generated during the adaptation and / or limitation of the first electric machine through increased generator-like operation is used by at least one further, second electric machine to drive at least one further drive train for propelling the vehicle, or that the additional energy required during the adaptation and / or limitation of the first electric machine for increased motor-like operation is additionally generated or less consumed by the second electric machine. Furthermore, a control unit for carrying out the procedure is described. While AWD / 4WD vehicles with a primary motor coupled to a multi-speed transmission fulfill their intended purpose, the object of the invention is to improve the perceived shift quality during a clutch-to-clutch shifting process in order to enhance the comfort and driving experience of the electric vehicle's occupants. Description of the invention The invention is defined by the claims. According to the invention, a method for shift control of an electric vehicle is provided. The electric vehicle comprises a multi-gear transmission that can receive a first motor torque from a first electric motor and deliver a first axle torque to a first axle. The multi-gear transmission includes at least one actuated clutch for selectively effecting a gear ratio change. The method comprises detecting a shift operation for the multi-gear transmission, actuating the at least one actuated clutch to effect the gear change, thereby generating a first axle torque oscillation in the first axle, and modulating a second electric motor to generate a second axle torque oscillation in a second axle, which is sufficient to compensate for the first axle torque oscillation in the first axle, thus reducing the overall oscillation of the vehicle acceleration and achieving high drive shift quality.The procedure further includes determining a percentage of the accelerator pedal travel when the shifting process is detected; retrieving a second electric motor calibration correlated with the determined percentage of the accelerator pedal travel; and applying the second electric motor calibration to modulate the second electric motor to generate the second axis torque oscillation in the second axis sufficient to compensate for the first axis torque oscillation in the first axis, thereby reducing the overall vehicle acceleration oscillation and achieving high drive shift quality. According to one embodiment, the method further comprises retrieving a clutch actuation calibration that correlates with the determined percentage travel of the accelerator pedal, and applying the clutch actuation calibration when actuating the at least one clutch to effect the gear change. According to a further embodiment, the method further comprises retrieving a first electric motor calibration that correlates with the determined percentage of the accelerator pedal travel, and applying the first electric motor calibration when modulating the first electric motor and actuating the at least one clutch to generate the first torque oscillation in the first axis. According to another embodiment, the second axis torque oscillation is phase-shifted relative to the first torque oscillation. According to a further embodiment, the method also includes an upshifting process during start-up, wherein the actuation of the at least one clutch includes a shifting process from clutch to clutch, which defines a torque phase followed by an inertia phase. According to another embodiment, the first electric motor calibration includes reducing the first motor torque during the inertia phase, and the second electric motor calibration includes increasing a second motor torque during the torque phase. According to another embodiment, the calibration of the second electric motor includes the modulation of the second motor during and after the inertia phase. A method for controlling the upshifting of a multi-gear electric vehicle during startup is provided according to several aspects. The method includes moving an accelerator pedal; detecting a shift operation for a multi-gear transmission designed to receive a first motor torque from a first electric motor and output a first axle torque to a first axle, the multi-gear transmission comprising a plurality of actuated clutches to effect a gear change ratio; determining a percentage of the accelerator pedal travel when the shift operation is detected; and retrieving a clutch calibration, a first electric motor calibration, and a second electric motor calibration that correlate with the determined percentage of accelerator pedal travel.Applying clutch calibration when actuating the multiple actuable clutches to effect the gear ratio, and applying first electric motor calibration when modulating the first electric motor, wherein the actuating of the multiple actuable clutches and the modulation of the first electric motor generates a first axis torque oscillation in the first axis; and applying second electric motor calibration when modulating the second electric motor to generate a second axis torque oscillation that is effective in compensating the first axis torque oscillation to reduce the overall vehicle acceleration oscillation and achieve high drive shift quality. In an additional aspect of the present disclosure, in which the actuation of the multiple actuable clutches comprises upshifting from clutch to clutch, defining a torque phase and an inertia phase, the modulation of the first electric motor comprises reducing a first motor torque during the inertia phase, and the modulation of the second electric motor comprises increasing a second motor torque during the torque phase. In another aspect of the present disclosure, the second electric motor calibration comprises the modulation of the second motor torque during the inertia phase and after the inertia phase to generate a second axle torque oscillation that is sufficiently phase-shifted to the first axle torque oscillation to dampen the vehicle acceleration oscillation of the electric vehicle. A method for a multi-speed electric vehicle shift control system for damping vehicle acceleration oscillation is provided, based on several aspects. The method involves determining a percentage of the accelerator pedal travel and subsequently retrieving clutch calibrations, a first electric motor calibration, and a second electric motor calibration, all correlated with that percentage. The method then applies the clutch calibration to actuate a change in the clutch ratio, thereby generating a first-axis oscillation, and applies the first electric motor calibration to modulate a first electric motor to dampen the vehicle acceleration oscillation. The clutch actuation and the first electric motor modulation together generate a first-axis torque oscillation.The method applies the second electric motor calibration during the modulation of the second electric motor to generate a second axis torque oscillation that is sufficiently phase-shifted to the first axis torque oscillation, thereby damping the vehicle acceleration oscillation of the electric vehicle. Further areas of application will become apparent from the present description. It should be understood that the description and specific examples serve only for illustration and are not intended to limit the scope of this disclosure. Brief description of the drawings The figures described here serve only for illustration and are not intended to limit the scope of this disclosure in any way. Fig. 1 is a functional diagram of an electric vehicle with a primary electric motor connected to a multi-speed transmission and an auxiliary electric motor, according to an exemplary embodiment; Fig. 2A is a diagram showing a first motor torque and a second motor torque during an upshift of the multi-speed transmission according to an exemplary embodiment; Fig. 2B is a diagram showing a first axle torque and a second axle torque during an upshift of the multi-speed transmission according to an exemplary embodiment; Fig. 2C is a diagram showing a vehicle acceleration oscillation of the electric vehicle during an upshift of the multi-speed transmission according to an exemplary embodiment; Fig.Figure 3A is a diagram showing controlled modulation of the first motor torque and controlled modulation of the second motor torque during upshifting of the multi-speed transmission according to an exemplary embodiment; Figure 3B is a diagram showing a first axle torque oscillation and a second axle torque oscillation generated by controlled modulation of the first and second motor torques, respectively, according to an exemplary embodiment; Figure 3C is a diagram showing a damped vehicle acceleration oscillation of the electric vehicle resulting from the second axle torque oscillation compensating the first axle torque oscillation, according to an exemplary embodiment; FigureFigure 4 is a block flow diagram showing a method for generating a lookup table that correlates a percentage of the accelerator pedal travel with a clutch-to-clutch calibration, a primary electric motor calibration, and an auxiliary motor calibration for controlling upshifting on start-up; and Figure 5 is a block flow diagram showing a method for controlling upshifting on start-up of a multi-speed electric vehicle. Detailed description The following description is merely exemplary and is not intended to limit the present disclosure, application, or use. The embodiments shown are disclosed with reference to the figures, where the same reference numerals denote corresponding parts in the different figures. The figures are not necessarily to scale, and some features may be exaggerated or reduced in size to show details of certain features. The specific structural and functional details disclosed should not be interpreted as limiting, but rather as a representative basis to show the person skilled in the art how the disclosed concepts are to be applied in practice. Figure 1 shows an example of an electric vehicle 100 configured for all-wheel drive (AWD) or all-wheel drive (4WD). The terms "electric vehicle" and "EV" are used interchangeably here and refer to a fully electric vehicle. The electric vehicle 100 can be any passenger or commercial vehicle, such as a car, truck, sport utility vehicle, crossover vehicle, van, minivan, taxi, bus, motorcycle, etc. The terms "AWD" and "4WD" are used synonymously here and refer to an EV drive system in which the front axle and rear axle are each driven by a separate electric motor. The electric vehicle 100 comprises an AWD / 4WD system 102 with a first electric motor 104 configured to selectively deliver a first motor torque output to a first axle 106 of the electric vehicle 100, and a second electric motor 108 configured to selectively deliver a second motor torque output to a second axle 110 of the electric vehicle 100. In the exemplary electric vehicle 100, the first axle 106 is represented as the rear axle 106 and the second axle 110 as the front axle 110, relative to a forward direction of travel of the electric vehicle 100. The first and second electric motors 104, 108 can be alternating current (AC) or direct current (DC) motors designed to deliver a relatively flat torque curve over a wide speed range. Each of the first and second electric motors 104, 108 is controlled via a power modulator 105 or 108 respectively.109 supplied so that the motor torque outputs of the first and second electric motors 104, 108 can be modulated independently of each other by a control unit 122, which is described in detail below. A typical multi-speed transmission used in an electric vehicle has two gears and is referred to as a two-speed transmission. An exemplary two-speed transmission may include a planetary gear set (not shown) and a pair of clutches that work together to selectively disengage and engage gear elements of the planetary gear set to shift from a first gear output to a second gear output, or vice versa. The shifting process, in which one clutch disengages a first gear element and the other clutch engages a second gear element to effect a gear change, is called a clutch-to-clutch shift. In the exemplary electric vehicle 100, the first electric motor 104 is coupled to a two-speed transmission 112, which has a first clutch 114 configured to selectively engage a first gear 116, and a second clutch 118 configured to selectively engage a second gear 120. In the embodiment shown, the two-speed transmission 112 is designed to transmit axle torque to the rear axle 106. However, it is understood that the two-speed transmission 112 can alternatively also transmit axle torque to the front axle 110. It is understood that the exemplary vehicle 100 is not limited to a specific transmission type or configuration, a specific number of gear stages, or a specific transmission type or configuration.Although, for example, a transmission with two gears is described, the transmission 112 can include more than two gears and contain all types of gears that can be selected by a clutch-to-clutch shift. The second gear ratio is higher than the first gear ratio, which means that in the second gear ratio the efficiency range of the vehicle 100 is effectively extended, thereby increasing the top speed of the electric vehicle 100 without the first electric motor 104 rotating faster or consuming more power. The torque / power generated by the electric motors 104, 108 can be modulated by a control unit 122. The control unit 122 determines the power (i.e., voltage, current, and waveform) that each of the power control modules 105, 109 supplies to the respective electric motors 104, 108, and thus the torque and power that each electric motor 104, 108 exerts on the axle 106, 110 to which it is coupled. To calculate the appropriate power that must be supplied to each motor to modulate the output torque of each motor, the control unit 122 receives data from a variety of sensors (not shown) and actuators throughout the vehicle 100, as well as vehicle calibration data from a lookup table stored in the control unit 122.In general, these sensors and actuators 124 include those used to monitor vehicle performance, those used to monitor the drive system, those used to monitor the condition and performance of the vehicle 100 and the power control electronics, and those used to monitor user inputs such as the percentage travel of an accelerator pedal 124 to control the torque / power output of the electric motors 104, 108 and thus the speed of the electric vehicle 100. The accelerator pedal 124 may be a conventional floor-mounted foot pedal 124, a steering wheel-mounted hand pedal 124 located near the steering wheel, or a lever 124 mounted on the steering wheel. The controller 122 can include one or more processors 124, a memory 126, and other components typically found in computer equipment. The memory 126 is a non-transitory, computer-readable medium that stores information accessible to the one or more processors 124, including instructions and data that can be executed by the processors 124 or otherwise used to implement a method 500, which is disclosed in detail below. The memory 126 can be of any type capable of storing information accessible to the processors 124, including a computer-readable medium or other medium that stores data readable by an electronic device, such as a hard disk drive, memory card, ROM, RAM, DVD or other optical discs, and other writable and read-only memory. Although only one control unit 122 is shown, the electric vehicle 100 can have multiple control units 122. The respective control units 122 can exchange various signals via a telematics server or CAN (Controller Area Network) communication 123. Each of the control units 122 can contain one or more processors, memory, and other components typically found in computer devices. Furthermore, each control unit 122 can control one or more systems, and a system can be controlled by multiple control units 122. For simplicity, the one or more control units 122 will be referred to as control unit 122 in the following. Clutch-to-clutch shifting is also known as single-transition shifting, meaning that only one disengaging clutch needs to be released and one engaging clutch needs to be engaged. Therefore, both clutches 114 and 118 must be controlled during the shifting process. The controlled synchronization of these two clutches 114 and 118 is performed by the control unit 122. There are four types of clutch-to-clutch shifting: upshifting on engagement, downshifting on engagement, upshifting on disengagement, and downshifting on disengagement. When torque / power is transmitted from the first electric motor 104 during clutch shifting, this type of shifting is called a power-on shift. The power-on upshift goes through a torque phase and then an inertia phase. One problem associated with power-on upshifting is the drop in motor torque at the end of the torque phase.The motor torque increases towards the end of the inertia phase, leading to an oscillation of torque at the output shaft after the end of the inertia phase, once the subsequent clutch is fully engaged. This sequence of events results in an abrupt fluctuation in the torque delivered by the driven axle and thus in a fluctuation in the vehicle acceleration of the electric vehicle 100. The abrupt fluctuation in torque delivered by the output shaft and the resulting fluctuation in vehicle acceleration during upshifting upon starting the engine reduce the driving comfort experienced by the occupants of the vehicle 100 and create the impression of poor-quality gear changes. Fig. 2A shows the torque output of the first electric motor 104 (dashed line), also referred to as the first motor torque, and the torque output of the second electric motor 108 (solid line), also referred to as the second motor torque, during a shift-up operation. Fig. 2B shows a first axle torque (dashed line), also referred to as the first axle torque, and a second axle torque (solid line), also referred to as the second axle torque, during the shift-up operation. Fig. 2C shows the oscillation of the vehicle acceleration during the shift-up operation with the ignition switched on. The units of the horizontal axes of Figs. 2A-2C are units of time (seconds), the units of the vertical axes of Figs. 2A and 2B are units of torque (newton-meters), and the units of the vertical axis of Fig. 2C are units of force (newton-meters).2C are accelerations (g), expressed as a ratio to the Earth's gravity. In Fig. 2A, the solid line represents the front engine torque and the dashed line the rear engine torque during an engaged upshift at 50% accelerator pedal travel. Accelerator pedal travel is defined as the percentage of displacement from 0 percent when the accelerator pedal 124 is in an unactuated state, to 100 percent when the accelerator pedal 124 is in a fully depressed state. For example, the percentage of accelerator pedal travel is 0 percent when the accelerator pedal 124 is in its highest position and 100 percent when the pedal is in its lowest position. The clutch-to-clutch shift begins at T=T0 and ends at T=TF. During clutch shifting, the torque of the rear engine increases by 202 before flattening out by 112 due to the change in the rear gear ratio, while the torque of the front engine remains relatively constant.In Fig. 2B, the solid line represents the torque at the front axle and the dashed line the torque at the rear axle during upshifting at 50% accelerator pedal travel. During the clutch change, the rear axle torque (dashed line) exhibits an abrupt fluctuation, while the front axle torque (solid line) remains relatively flat. The abrupt amplitude and frequency fluctuation of the rear axle torque causes an abrupt oscillation in the acceleration of the electric vehicle 100, as shown in Fig. 2C. This abrupt oscillation in the electric vehicle's acceleration is perceived as poor transmission shift quality. Fig. 3A shows the torques of the first and second motors during a controlled upshift upon engagement, Fig. 3B shows the torques of the first and second axles during a controlled upshift upon engagement, and Fig.Figure 3C shows the vehicle acceleration oscillation during controlled upshifting upon startup. The upshifting upon startup is controlled in such a way as to minimize the vehicle acceleration oscillations at 50% accelerator pedal travel. Referring to Fig. 3A, the rear electric motor is modulated during controlled upshifting to minimize the abrupt amplitude fluctuation of the rear axle torque caused by shifting from clutch to clutch (see Fig. 3B). The first modulation of the electric motor initially comprises a reduction of the first motor torque at setpoint 302 in the torque phase, followed by an increase of a first motor torque at setpoint 304 in the inertia phase. As shown in Fig. 3A, the front electric motor 108 is simultaneously modulated by temporarily increasing its torque during the torque phase at reference 306 and again at references 308 and 310 during and after the inertial phase to generate a front axle torque oscillation that at least partially compensates for the rear axle oscillation. The front axle torque oscillation is sufficiently phase-shifted relative to the rear axle torque oscillation to effectively dampen the vehicle's acceleration oscillation. Preferably, the front axle torque oscillation is phase-shifted with the rear axle torque oscillation in both amplitude 312A, 312B and frequency 314A, 314B, as shown in Fig.Figure 3B shows that the phases of the two waves are completely opposite and have the same amplitude, so that they cancel each other out to achieve a smoother vehicle acceleration that is perceived by the occupants of the electric vehicle. The modulation of the front electric motor generates a torque oscillation at the front axle, which is able to balance the torque oscillation at the rear axle in order to smooth out the acceleration oscillation of the vehicle during upshifting, resulting in a smoother and therefore higher quality shifting process for the occupants, as shown in Fig. 3C. The calibration of the rear engine modulation, also referred to as rear engine calibration, sufficient to minimize the sudden amplitude fluctuation of the rear axle torque caused by clutch-to-clutch shifting, can be performed experimentally beforehand and stored in a lookup table. Control unit 122 can access and execute this calibration when it detects an upshift command upon power-on. Similarly, the calibration of the front engine modulation, also referred to as front engine calibration, sufficient to generate a front axle torque oscillation capable of compensating for the rear axle torque oscillation to smooth vehicle acceleration oscillation, can be performed experimentally beforehand and stored in the lookup table.The calibration of the clutch actuation pressures and timing to effect clutch-to-clutch shifting, also known as clutch actuation calibration, can be performed experimentally beforehand and stored in the lookup table. Rear engine calibration, front engine calibration, and clutch actuation calibration can be performed for predetermined increments of accelerator pedal travel, preferably at least every 10%, from 0% to 100% of the travel. Fig. 4 is a block flow diagram of method 400 for generating a lookup table for use in method 500 for upshift control of an electric vehicle to ensure a high-quality shift feel. The presented method relates to a two-speed transmission 112 connected to the rear electric motor 104. It should be understood that methods 400 and 500 are also applicable to a two-speed transmission 112 connected to the front electric motor 108 as opposed to the rear electric motor 104. Procedure 400 begins in block 402 with the operation of the electric vehicle 100 in rear-wheel drive mode, in which little to no electrical power is supplied to the front electric motor 108, or in AWD / 4WD drive mode, in which electrical power is supplied to both the rear and front electric motors 104, 108. In block 404, the control unit 122 monitors the transmission 112 for a shift-up event, such as a request for a gear change, a predicted need for a gear change, or an event that triggers a need for a gear change. If no shift-up event is detected during shift-up, procedure 400 returns to block 402. Returning to Block 404: When an upshift event is detected, the procedure proceeds to Block 406, where the percentage of accelerator pedal travel is recorded and the clutch actuation pressures and timings are calibrated to minimize the abruptness of the disengaging clutch and engaging clutch to effect a gear change. The clutch actuation calibration is recorded in relation to the percentage of accelerator pedal travel. In block 408, the modulation of the rear electric motor is calibrated to reduce the inertia phase of the rear axle torque increase, resulting in rear axle torque with smaller amplitude and frequency fluctuations. In block 410, the front electric motor is calibrated to compensate for the rear axle torque oscillation by generating a front axle torque oscillation sufficient to counteract the rear axle torque oscillation, thereby reducing the overall vehicle acceleration oscillation and achieving high shift quality. In block 412, the resulting vehicle acceleration oscillation, generated from the rear engine calibration, the front engine calibration, and the clutch actuation calibration, is evaluated to determine if it meets a predefined shift quality. If not, procedure 400 can return to blocks 406, 408, and 410. If the quality is satisfactory, the procedure proceeds to block 414 and terminates. This procedure 400 is repeated for a specified percentage of accelerator pedal travel. For example, this procedure 400 can be repeated for every 10% of accelerator pedal travel from 0% to 100% to create a lookup table that relates a percentage of accelerator pedal travel to a rear engine calibration, a front engine calibration, and a clutch actuation calibration. Fig. 5 shows a block flow diagram of a Method 500 for an AWD / 4WD electric vehicle for controlling upshifting on power-up to ensure a high-quality shift feel by reducing vehicle acceleration oscillations during upshifting on power-up. Referring to the electric vehicle 100 of Fig. 1 and the method 500 of Fig. 5, the method 500 begins in block 502 when the electric vehicle 100 is in driving mode and is driven by at least one electric motor 104 and a second electric motor 108. In block 504, the control unit 122 monitors the multi-speed transmission 112 for a shift-up event. If the control unit 122 does not detect a shift-up event during the start-up, the method returns to block 502. Returning to Block 504: When the control unit 122 detects a shift-up event, the procedure proceeds to Block 506, in which the control unit 122 determines the percentage of accelerator pedal travel being applied. Using the calibration lookup table generated from the procedure 400 described above and illustrated in Fig. 4, the control unit 122 retrieves a rear engine calibration, a front engine calibration, and a clutch actuation calibration corresponding to the determined percentage of accelerator pedal travel. In block 508, the control unit 122 applies the clutch actuation calibration to the disengaging and engaging clutches to effect the change in the speed ratio. Simultaneously, in block 510, the control unit 122 applies the rear electric motor calibration to modulate the rear electric motor, while simultaneously applying the front electric motor calibration to modulate the front electric motor. The modulation of the front motor generates a torque oscillation at the front axle sufficient to compensate for the torque oscillation at the rear axle caused by the combination of clutch actuation and rear electric motor modulation, thus reducing the vehicle's acceleration oscillation. Return to Fig.3B: The modulation of the front electric motor generates a sinusoidal front axle torque oscillation that is phase-shifted with the sinusoidal rear axle torque oscillation, thereby damping the vehicle acceleration oscillation during upshifting when switching on. In block 512, the upshift is completed upon startup, and the vehicle continues in driving mode. The process returns to block 502 and repeats process 500. The present disclosure can more effectively reduce acceleration oscillations during upshifting in an electric vehicle 100, which is driven by a first electric motor 104 connected to a multi-speed transmission and a second electric motor 108. The reduction of acceleration oscillations during upshifting gives the occupants of the electric vehicle 100 the impression of a smoother and higher-quality shifting experience without any additional structural costs for the vehicle 100. The concept described above of using the front motor to control the torque oscillation of the front axle in order to compensate for the torque oscillation of the rear axle during upshifting can be similarly applied to other types of shifting operations, including downshifting on engagement, upshifting on disengagement, and downshifting on shutdown.

Claims

Method (400, 500) for shift control of an electric vehicle (100), comprising: detecting (404, 504) a shift operation for a multi-gear transmission (112) with at least one actuated clutch (114, 118) for selectively effecting a gear ratio change, wherein the multi-gear transmission (112) is designed to receive a first motor torque from a first electric motor (104) and to deliver a first axle torque to a first axle (106); actuating (508) the at least one actuated clutch (114, 118) to effect the change in the gear ratio, thereby generating a first axle torque oscillation in the first axle (106);Modulating (408) a second electric motor (108) to generate a second axis torque oscillation in a second axis (110) sufficient to counteract the first axis torque oscillation in the first axis (106) to reduce vehicle acceleration oscillation of the electric vehicle (100); Determining (406, 506) a percentage travel of an accelerator pedal (124) when the shift operation is detected; Retrieving (506) a second electric motor calibration correlated with the determined percentage travel of the accelerator pedal (124); and Applying (510) the second electric motor calibration when modulating the second electric motor (108) to generate the second axis torque oscillation in the second axis (110). Method (400, 500) according to claim 1, further comprising: retrieving (506) a clutch actuation calibration that correlates with the specified percentage travel of the accelerator pedal (124); and applying (510) the clutch actuation calibration when actuating the at least one clutch (114, 118) to effect the gear change. Method (400, 500) according to claim 2, further comprising: retrieving (506) a first electric motor calibration that correlates with the determined percentage travel of the accelerator pedal (124); and applying the calibration of the first electric motor (104) during the modulation of the first electric motor (104) and the actuation of the at least one clutch (114, 118) to generate the first torque oscillation in the first axis (106). Method (400, 500) according to claim 3, wherein the second axis torque oscillation is out of phase with the first torque oscillation. Method (400, 500) according to claim 3, wherein the switching process includes up-switching on. Method (400, 500) according to claim 3, further comprising an upshifting during switching on, wherein the actuation (508) of the at least one clutch (114, 118) comprises a switching operation from clutch (114, 118) to clutch (114, 118) which defines a torque phase followed by an inertia phase. Method (400, 500) according to claim 6, wherein the calibration of the first electric motor (104) comprises reducing the first motor torque during the inertia phase and wherein the calibration of the second electric motor (108) comprises increasing a second motor torque during the torque phase. Method (400, 500) according to claim 7, wherein the calibration of the second electric motor (108) comprises modulating the second electric motor (108) during the inertia phase. Method (400, 500) according to claim 8, wherein the calibration of the second electric motor (108) further comprises the modulation of the second electric motor (108) after the inertial phase.

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